Color display devices are typically multi-channel devices in the sense that multiple physical color channels represent every pixel on the display. Multi-channel display devices include cathode ray tubes (CRT), liquid crystal displays (LCD), plasma displays, and other imaging devices. One common example of a multi-channel device is a three channel device comprising red, green, and blue (RGB) channels.
Each of the color channels in a multi-channel display device may be modeled as a combination of a light source and a light valve. In the case of the LCD, the light source typically comprises a common backlight and color filters for each of the channels. The light valve, in the case of an LCD, comprises one or two fixed polarizers and liquid crystal cells (LCC), which rotate a polarization plane of passing light to regulate the amount of light emitted from the display.
An emission spectrum for the light source is useful for spectral modeling and display calibration to improve color accuracy of imagery presented by the display. However, the light source emission spectrum is usually unknown, partially because the spectra of light sources vary between different manufacturers and models of display devices and from device to device. Further, the emission spectrum for a light source may change over time due to component aging, especially in the case of an LCD, which uses luminescent lamps as the common backlight.